My powerful Linux desktop (12 core, 32GB RAM, SSD, fast processor, ubuntu 13.10) slows down to a crawl when I rsync from my internal drive to an attached USB3 NTFS drive. Typing any command, like "df" or "ls", takes 5-10 seconds to respond. The slow feel reminds me of a heavily swapping computer, but the "free" command says swap size is zero, with 29GB of RAM free (buffers). "uptime" shows a load average of about 4.0, and "top" shows that the top processes are the rsync commands. I also see kswapd0 in the top few processes, but no swap space is being used and there's tons of free RAM.

The slowdown occurs even when I run rsync at a "nice" level of 19. The slowdown also lasts for about 1-2 minutes after I kill the rsync.

The slowdown doesn't happen with my other ext4 USB3 disk.

The actual transfer rate to the USB disk is fine: it is not slow. I'm asking about the heavy impact on the usability of the system during the rsync. Anybody know why this happens and how to prevent it?

1 Answer
1

Answering my own question: the answer is "user error." The whole USB/NTFS thing was a red herring!

My rsync command was supposed to back up my internal drive to an external USB drive, like this:

$ rsync -avx / /media/backupdrive

After a recent OS upgrade, however, Ubuntu changed the auto-mounted destination to /media/username/backupdrive, inserting my username into the path. So, my script was not actually hitting the USB drive, but writing to /media locally on my boot drive.

In other words, my boot drive (an SSD) was being hammered by rsync and filling up to 100%. This caused the system slowness.